656 GEOLOGY OP OLD HAMPSHIRE COUNTY, MASS. 



troughs having their source in the same place and at the same level, but having dif- 

 ferent slopes. The water in the one having the least slope must be above the level of 

 the water in the other at all points directly opposite. 



The difference in slope of the two valleys, together with the narrowness of the 

 gap in the Divide range, seem to be the cause of the greater height of the water in 

 this vicinity. 



It seems that the fonowing- considerations should be weighed in seeking 

 for an explanation of this curious difference of level: 



(1) The Springfield basin is about four times as wide as the Westffeld, 

 and thus much more material would be required to fill it up to the same level. 



(2) Because of the northwestern recession of the ice the eastern floods 

 sent the mass of their sands down through the Monson-Willimantic Valley 

 or lodo-ed them in the great series of catchment basins I have described 

 above as the eastern series of glacial lakes. 



(3) The same recession of the ice, continued northwestwardly, caused 

 the heaviest floods to pour into the lateral or Westfield Valley by all the 

 transverse valleys coming in from the west, and of these the Westfield River 

 was the most important, because it runs back northwest across the whole 

 plateau of the Berkshire Hills and at Dalton opens broadly into the great 

 Housatonic Valley, and because it remained the main trunk of the ice 

 di-ainage until the ice had receded from those hills; and while the ice front 

 was in the region of Pittsfield the di'ainage of a portion of the Upper Housa- 

 tonic was deflected into this valley, producing the interesting sand plains in 

 the upper valley at Hinsdale and bringing down bowlders from this region 

 to spread over the Westfield plain. 



The combined effect of these three conditions seems sufficient to explain 

 the lower level of the eastern plahi,and instead of saying that "the flood at 

 Westfield was at least 48 feet higher than that at Springfield," I should say 

 that the waters were 48 feet shallower in the Westfield basin than over 

 Springfield. 



Where kame sands were heaped up in the Springfield basin the high 

 teiTace is notched in them at nearly the same height as in the Westfield 

 basin; as, for example, on the extreme east of the basin in Wilbraham or 

 north in Holyoke. At the notch in the Divide Range occupied by the West- 

 field River the exact svu-face of the lake bottom has, of course, been 

 removed by the later erosion of the river; but at the next notch south, at 

 Risings, just on the State line, the surface is well preserved and is very 

 instructive. It is what might be expected on the assumption of a narrow 



